To define more precisely the differentiating risk factors for arrhythmic death (ARD), circulatory failure death (CFD), and non-fatal myocardial infarction (MI), follow-up data will be collected through 6/30/84 on 743 men, age 40-65 at intake, who have been followed previously through 1020 5-year observation periods with 1-7 comprehensive examinations and ECG tape recordings, and investigation of 82 ARD and 60 CFD. Present findings indicate that ARD, CFD, and non-fatal MI are significantly different with respect to the preceding presence or absence of, and the nature of 1) myocardial disorders; 2) disorders of cardiac rate, rhythm, conduction, and repolarization; and 3) non-cardiac risk factors, both 5 years before the event and at the time of the event; that they are different in the nature of the factors that precipitate the event; and that risk factors present at the initial examinations are significantly predictive for 10 years. The additional follow-up will yield 10-year data on all men and 20-year data on 301 men, and an estimated 99 ARDs, 68 CFDs and 34 acute non-fatal MIs, which will be analyzed in relation to data at the beginning of 5 and 10-year observation periods. Detection of interactions of variables which affect the outcome will be significantly enhanced and the degree of uncertainty of present estimates of risk, arising from the relatively small number of deaths and new events hitherto available for analysis, will be reduced. The additional period of support will make possible a more complete analysis of the intervening steps which proceed to one or none of the three outcomes, and the better identification of developments that indicate that the nature or magnitude of the risk has changed significantly.